1. Field of the Invention
This invention concerns aqueous solutions of dis- and tris-azo dyes prepared from diaminostilbenedisulfonic acid.
2. Description of the Prior Art
Various dyes have been made from diaminostilbenesulfonic acid. See, for instance, U.S. Pat. No. 2,489,463, German Pat. No. 55,648, and Japanese Pat. No. 20,080/64.
Regarding making dyes and producing commercial strength solutions by packaging an adjusted reaction mass, see U.S. Pat. No. 3,621,008, U.S. Pat. No. 3,600,376, U.S. Pat. No. 3,681,320. The processes of the latter two patents involve substitution of lithium or triethanolammonium ions in place of at least some of the usual sodium ions present in the diazotization and coupling masses involved. The dye processes of these patents are of the type A.fwdarw.B.rarw.C where B is 6,6'-ureylenebis-1-naphthol-3-sulfonic acid.
U.S. Pat. No. 2,475,265 discloses isolation of the tetrazonium salt of 3,3'-dihydroxybenzidine. No dye solution is formed and the precipitated dye is separated by filtration.